1. Field of Invention
The invention relates, generally, to an electric machine and, more particularly, to such a machine that has a stator winding with rigid bars and a method of construction thereof.
2. Description of Related Art
Traditionally, the stator winding of an electric machine is made by filiform and flexible conductors that are initially coil-wound. Then, the coils are telescoped into the stator slots and are, hence, electrically connected to one another. Such a construction method is complex to automate as it is very difficult to automatically telescope the coils inside the stator slots as the coils do not have a stable shape and should be deformed to pass through the small axial aperture of the slots.
To overcome the construction difficulties of the stator winding made by filiform and flexible conductors, a stator winding made by rigid bars was proposed. In a stator winding made by rigid bars, a series of rigid bars are used that are initially “U”-shaped and, hence, axially telescoped into the stator slots—thus forming an entry side, in which the cusps of the “U”-shaped bars are arranged, and an exit side, in which the legs (i.e., the straight sections) of the “U”-shaped bars are arranged. Once all the bars have been telescoped into the stator slots, the legs on the exit side are twisted (by an operation called “twisting”), and, hence, the free ends of the legs are connected to one another by welding to form the electrical paths of the stator winding.
It has been proposed to differentiate the sizes of the cusps of the “U”-shaped bars in such a way to obtain, due to such a differentiation, the electrical paths of the stator winding 8. However, differentiating the sizes of the cusps of the “U”-shaped bars involves significant complications both in making the “U”-shaped bars (as at least two different types of “U”-shaped bars should be made) and inserting the “U”-shaped bars into the stator slots (as there is a need to manage at least two different types of “U”-shaped bars that have to be telescoped into accurate and predetermined positions and are in no way interchangeable with each other).
During the construction of the stator winding, it has been proposed to unite all the “U”-shaped bars at the outside of the stator magnetic core and, hence, insert all the “U”-shaped bars into the stator slots with a single movement. However, a push of high intensity is simultaneously exercised on all the “U”-shaped bars, and, hence, it is possible that one or more “unfortunate” “U”-shaped bars is/are subjected to an excessive push (i.e., too strong) and/or improperly directed, which induces damage to the external insulating enamel that covers the “U”-shaped bars themselves.
Patent Application US2003024101A1 describes an electric machine having a stator winding with rigid bars and a related method of construction.
Thus, there is a need in the related art for an electric machine having a stator winding with rigid bars and a method of construction thereof. More specifically, there is a need in the related art for such electric machine and method that are easy and affordable to obtain.